Masakazu Fukuta

Effect of Alpinia zerumbet components on antioxidant and skin diseases-related enzymes

BackgroundThe skin is chronically exposed to endogenous and environmental pro-oxidant agents, leading to the harmful generation of reactive oxygen species. Antioxidant is vital substances which possess the ability to protect the body from damage cause by free radicals induce oxidative stress. Alpinia zerumbet, a traditionally important economic plant in Okinawa, contains several interesting bioactive constituents and possesses health promoting properties. In this regard, we carried out to test the inhibitory effect of crude extracts and isolated compounds from A. zerumbet on antioxidant and skin diseases-related enzymes.MethodsThe antioxidant activities were examined by DPPH, ABTS and PMS-NADH radical scavenging. Collagenase, elastase, hyaluronidase and tyrosinase were designed for enzymatic activities to investigate the inhibitory properties of test samples using a continuous spectrophotometric assay. The inhibitory capacity of test samples was presented at half maximal inhibitory concentration (IC50).ResultsThe results showed that aqueous extract of the rhizome was found to have greater inhibitory effects than the others on both of antioxidant and skin diseases-related enzymes. Furthermore, 5,6-dehydrokawain (DK), dihydro-5,6-dehydrokawain (DDK) and 8(17),12-labdadiene-15,16-dial (labdadiene), isolated from rhizome, were tested for antioxidant and enzyme inhibitions. We found that DK showed higher inhibitory activities on DPPH, ABTS and PMS-NADH scavenging (IC50 = 122.14 ± 1.40, 110.08 ± 3.34 and 127.78 ± 4.75 μg/ml, respectively). It also had stronger inhibitory activities against collagenase, elastase, hyaluronidase and tyrosinase (IC50 = 24.93 ± 0.97, 19.41 ± 0.61, 19.48 ± 0.24 and 76.67 ± 0.50 μg/ml, respectively) than DDK and labdadiene.ConclusionOur results indicate that the rhizome aqueous extract proved to be the source of bioactive compounds against enzymes responsible for causing skin diseases. Moreover, DK could be used as a potent inhibitor and be further exploited to be used in anti-skin disease formulations.

Comparative efficacies in vitro of antibacterial, fungicidal, antioxidant, and herbicidal activities of momilatones A and B

Abstract Momilactones A (MA) and B (MB) are phytoalexins derived from rice plant (Oryza sativa) and were considered to be a part of the mechanism of rice self-defense system. The present study was to evaluate the comparative efficacies in vitro of antibacterial, fungicidal, antioxidant, and herbicidal activities of MA and MB. In general, MB shows higher antifungal, antibacterial, and herbicidal action than MA, although its antioxidant property was less than MA. In herbicidal trial, the IC50 values of MB against germination, shoot and root elongation of barnyardgrass and monochoria were 40.9, 45.5, and 27.5, and 27.1, 17.3, and 0.9 µg, respectively. For MA, these values were 40.3, 35.6, and 55.1, and 43.9, 24.3, and 0.5 µg, respectively. For antifungal activity, momilactone B (IC50: 1.2, 123.9, and 53.4 µg) exerted significantly greater inhibition than MA (IC50: 78.1, 198.1, and 95.3 µg) against Botrytis cinerea, Fusarium solani, Colletrotrichum gloeosporioides, respectively, except for Fusarium oxysporum that both MA and MB showed no marked difference. In addition, MB exhibited significantly stronger antibacterial activity than MA against Pseudomonus ovalis, Bacillus cereus, and Bacillus pumilus, whereas the inhibitory activity of the two compounds was similar against Escherichia coli. Both MA and MB exerted rather weak antioxidant activity (EC50 was 783.9 and 790.7 µg, respectively), of which MA showed a slightly stronger antioxidant activity than MB. This study is the first to examine antifungal, antibacterial, and antioxidant activities of two phytoalexins, as well as their comparative efficacies against growth of the noxious weeds barnyardgrass and monochoria.

Chemical Interaction in the Invasiveness of Cogongrass (Imperata cylindrica (L.) Beauv.)

From gas chromatography-mass spectrometry (GC-MS), numerous plant growth inhibitors were found in the rhizome and root exudates of cogongrass, one of the most problematic weeds in the world. iso-Eugenol, iso-ferulic acid, linoleic acid, ferulic acid, and vanillin were the major chemicals in the rhizome (88.1-392.2 microg/g of fresh root), while 4-acetyl-2-methoxyphenol was the principle substance (872.6 microg/plant) in the root exudates. In fields, the use of cutting and plowing reduced weed biomass and weed density of cogongrass >70%. However, the alternative invasion of beggar tick might be a problem, because its density and biomass increased 33.3 and 62.5%, respectively. Chemicals from cogongrass showed selective effects against tested invasive species. Of them, 2,4-di-tert-butylphenol was the most potent (78.3-100% of inhibition), followed by iso-eugenol and 4-acetyl-2-methoxyphenol. These compounds may play important roles in the invasiveness of cogongrass and might be promising parent constituents of synthesis to develop novel herbicides for control of invasive plants.

Antiatherogenic Properties of Acetone Extract of Alpinia zerumbet Seeds

Oxidation of low-density lipoprotein (LDL) is the principal risk factor for the development of atherosclerosis. In this study, we used several methods to investigate the ability of the acetone extract from rhizomes, stems, leaves, flowers, pericarps and seeds of Alpinia zerumbet to inhibit atherosclerosis in vitro. The seed extract had the strongest activity against tyrosinase, pancreatic lipase (PL), 15-lipoxygenase (15-LO) and LDL oxidation activities (IC50 = 2.30 ± 0.02, 5.00 ± 0.07, 1.29 ± 0.07 and 15.40 ± 0.86 µg/mL, respectively), amongst all different parts. It also had similar effects to the positive controls. Most of the extracts showed partial agonistic properties towards estrogenic activity. Cholest-4-ene-3,6-dione, a steroid present only in the seed extract seems to be the compound responsible for these activities. The results showed that cholest-4-ene-3,6-dione had similar ability to curcumin and quercetin against PL and LDL oxidation (IC50 = 19.50 ± 1.17 and 16.12 ± 1.43 µg/mL, respectively). Furthermore, cholest-4-ene-3,6-dione (IC50 = 34.21 ± 1.31 µg/mL) had higher inhibition against 15-LO than quercetin (IC50 = 54.79 ± 1.12 µg/mL).

Solid-Phase Synthesis of Mimosine Tetrapeptides and Their Inhibitory Activities on Neuraminidase and Tyrosinase

Neuraminidase is a rational target for influenza inhibition, and the search for neuraminidase inhibitors has been intensified. Mimosine, a nonprotein amino acid, was for the first time identified as a neuraminidase inhibitor with an IC(50) of 9.8 ± 0.2 μM. It was found that mimosine had slow, time-dependent competitive inhibition against the neuraminidase. Furthermore, a small library of mimosine tetrapeptides (M-A(1)-A(2)-A(3)) was synthesized by solid-phase synthesis and was assayed to evaluate their neuraminidase and tyrosinase inhibitory properties. Most of the tetrapeptides showed better activities than mimosine. Mimosine-FFY was the best compound, and it exhibited 50% neuraminidase inhibition at a low micromolar range of 1.8 ± 0.2 μM, whereas for tyrosinase inhibition, it had an IC(50) of 18.3 ± 0.5 μM. The kinetic studies showed that all of the synthesized peptides inhibited neuraminidase noncompetitively with K(i) values ranging from 1.9 -to 7.2 μM. These results suggest that mimosine could be used as a source of bioactive compounds and may have possibilities in the design of drugs as neuraminidase and tyrosinase inhibitors.

Significant longevity-extending effects of Alpinia zerumbet leaf extract on the life span of Caenorhabditis elegans.

The beneficial effects of the phytochemical compounds in fruits and vegetables have been extrapolated mainly from in vitro studies or short-term dietary supplementation studies. Recent approaches using animal models of Caenorhabditis elegans are becoming quite popular, and in this regard the effects of Alpinia zerumbet leaf extract (ALP) on C. elegans lifespan were investigated under both normal and stress conditions. ALP significantly increased, mean lifespan by 22.6%, better than the positive control, resveratrol. Furthermore, both under thermal and oxidative stressed conditions, ALP increased the survival rate significantly better than quercetin. Further studies indicated that the significant longevity-extending effects of ALP on C. elegans can be attributed to its in vitro free-radical scavenging effects and its upregulation of stress-resistance proteins, including superoxide dismutase 3 (SOD-3) and heat-shock protein (HSP-16.2). These results suggest that phytochemical compounds in A. zerumbet have beneficial effects on the lifespan of C. elegans, and that they can be used as a source of dietary supplements for aging and age-related diseases.

Temperature threshold of isoprene emission from tropical trees, Ficus virgata and Ficus septica.

This paper describes the existence of temperature threshold in isoprene emission from tropical trees for the first time. Isoprene emission capacity of Ficus virgata leaves kept outdoors were measured over a period of 20 d in the wintertime. When the plants experienced the low temperature below 12 °C in the daytime, isoprene emission was completely suppressed, and re-activated by elevated temperature above the threshold of 12 °C. Photosynthesis is also decreased similarly, but too much smaller extent compared to the reduction observed for isoprene emission. The cut off level of accumulated temperature to shut off the isoprene emission was roughly estimated to be 300 degree/d. The shut off in the isoprene emission by the low temperature was confirmed experimentally by use of phytotron with tropical trees of F. virgata and F. septica. Isoprene emission of both species ceased at 12 °C, and re-activated by raising the temperature above the threshold level. Photosynthesis was lowered slightly as was the case for the field observation, and no close association between photosynthesis and isoprene emission was noted. The expression of isoprene synthase gene showed much greater variation after exposure to the cold temperature compared to those involved in photosynthesis. These observations therefore suggested the existence of putative direct connection between perception of temperature and isoprene emission in tropical trees, which may merit further investigation to estimate the net output of isoprene from subtropical or tropical forest.

Temperature controls on the basal emission rate of isoprene in a tropical tree Ficus septica: exploring molecular regulatory mechanisms

Isoprene emission from plants is very sensitive to environmental temperature both at short-term and long-term scales. Our previous study demonstrated suppression of isoprene emission by cold temperatures in a high emitting tropical tree Ficus septica and revealed a strong correlation of emission to isoprene synthase (IspS) protein levels. When challenged with decreasing daily temperatures from 30 to 12 °C, F. septica completely stopped isoprene emission at 12 °C, only to recover on the second day after re-exposure to 30 °C. Here, we explored this regulation of isoprene emission in response to environmental temperature by a comprehensive analysis of transcriptome data, gene expressions and metabolite pools of the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway. MEP pathway genes and metabolites dynamics did not support substrate-level limitations as major control over observed basal emission, but transcriptome data, network inferences and putative regulatory elements on IspS promoter suggested transcriptional regulation of IspS gene through circadian rhythm and phytohormone signalling processes. Expression levels of 29 genes involved in these pathways were examined by quantitative real-time PCR. We propose that temperature controls over basal isoprene emission at a time-scale of hours to few days are regulated by phytohormone-mediated transcriptional modulation of IspS gene under synchronization by the circadian clock.